1. Field of the Invention
This invention relates to a data communication apparatus, particularly relates to a data communication apparatus which ensures data communications with a plurality of sites.
2. Description of the Prior Art
In a general data communication between data communication apparatuses, a communication parameter is set on the basis of a result of training performed between modems of the data communication apparatuses, then communications are taken place by referring to the parameter. A data communication rate is given as one example of communication parameters. When the modem installed in the data communication apparatus corresponds to the communication standard V.32, a data communication rate is determined among data communication rates such as 33.6 Kbps at maximum, 31.2 Kbps, or 28.8 Kbps etc. depending on the training between both of the modems, and the data communication is taken place at that data communication rate.
There has been an increase in types and standards of modems in recent years, and it causes a problem that mutual linkage is not established within a training time prescribed by both modems, and thus a data communication can not be held.
A data communication is taken place through a communication network. For example, as shown in FIG. 5, when the own data communication apparatus 51 transmits data to an A-site 53 in a short distance, the data transmitted from the data communication apparatus 51 is sent to the A site 53 through a communication line 61, an X-exchange 52, and a communication line 62. When the own data communication apparatus 51 transmits data to a far B-site 55 and communication lines 63 and 64 are available, the data communication apparatus 51 transmits data to the B-site 55 through the direct way; through the communication line 61, the X-exchange 52, the communication line 63, a Y-exchange 54, and the communication line 64. When the communication lines 63 and 64 are not available, the data communication apparatus 51 transmits data to the B-site 55 through the communication line 61, the X-exchange 52, a communication line 65, a Z-exchange 56, and a communication line 66, avoiding the communication lines 63 and 64.
In case, as shown in FIG. 5, of a far distance communication or a complicated communication path such that the data is transmitted through the communication line 61, the X-exchange 52, the communication line 65, the Z-exchange 56, and a communication line 66, an error is likely to occur, causing unsuccessful data communication. In addition, in case that a communication status is not good even at a distance is short and a data communication rate is fast, an error is likely to occur, causing unsuccessful data communication.
The present invention was made to provide a data communication apparatus ensuring a link between sites. Furthermore, the present invention was made to provide a data communication apparatus capable of conducting a secure data communication irrespective of a line distance between the sites or a communication line status.
To achieve the above objective, a data communication apparatus, according to the present invention, for conducting a data communication with a plurality of sites on a basis of a predetermined communication parameter comprises storage means for storing a communication parameter used for a data communication and a result of the data communication conducted by the communication parameter, and control means for reading out an optimum communication parameter corresponding to a site with which a data communication is conducted from the storage means and conducting a data communication on the basis of the communication parameter.
The storage means stores a communication parameter used for a data communication and result information on whether the data communication conducted by the communication parameter succeeded or not for each site.
The control means reads out an optimum communication parameter corresponding to a site from the storage means and conducts a data communication on the basis of the communication parameter. By these procedures, a link between sites is ensured and furthermore, a data communication is conducted securely irrespective of a line distance between the sites and a line status.
In the data communication apparatus according to the present invention, the storage means stores a time when a data communication is conducted, and the control means reads out an optimum communication parameter corresponding to a site and a communication time from the storage means and conducts a data communication on the basis of the communication parameter.
Therefore, the storage means stores a time when the data communication is conducted for each site, in addition to a communication parameter and information on whether a data communication succeeded or not. When a data communication is conducted with a site, an optimum communication parameter is read out from the storage means corresponding to a site and a communication time, and a data communication is conducted by the communication parameter. Therefore, a link between sites is secured, and a data communication is conducted securely irrespective of a line distance between sites and a line status.
In the data communication apparatus according to this invention, the storage means stores a data communication rate as one of the communication parameters, and the control means reads out a communication parameter by referring to the stored data communication rate and conducts a data communication.
Therefore, the storage means stores a data communication rate as one of the communication parameter. When a data communication is conducted with a site, a communication parameter is read out by referring to a data communication rate at which a data communication succeeded, and a data communication is conducted by that communication parameter. A link between sites is ensured and a data communication is conducted securely irrespective of a line distance between sites and a line status.